If there are two time periods the difference-in-differences model is
simply a cross-sectional regression estimated by OLS. When there are
multiple periods it becomes a pooled-OLS regression (although it is
advised to add time period dummy variables). These estimation methods
can be accessed via the appropriate menus (or code) that are provided as
standard in STATA. However, it is important to specify the variables in
the model correctly. A very good treatment of this model is provided in
chapter 13 of Wooldridge (2006) "Introductory Ecoonometrics A Modern
Approach" South-Western (4th edition).
Thanks,
Chris
醫事室明傑ntu wrote:
> Dear statalis :
> Where may search difference in difference sample code?
> Because I need to run that?
>
> Thanks
> Mingchei lin
--
===============================
Dr Chris Stewart,
Economics Subject Group,
London Metropolitan Business School,
London Metropolitan University (City campus),
84 Moorgate, London, EC2M 6SQ,
United Kingdom.
Tel. 44 (0)20 7320 1651 (x69 1651)
Fax. 44 (0)20 7320 1585
e-mail: [email protected]
web.
http://www.londonmet.ac.uk/lmbs/subjects/economics/staff/chris-stewart.cfm
===============================
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